The present invention relates to a burner adapted to burn a solid/liquid mixed fuel (a slurry/fuel) such as a coal/water mixed slurry (CWM), coal/oil mixed slurry (COM), coal/methanol mixed slurry (CMM) or the like or a liquid fuel, and more particularly a burner which is compact in size and capable of atomizing a fuel and withstanding wear.
Coal slurry fuels are atomized and sprayed by a burner. Conventionally, as shown in FIGS. 1 and 2, such burner k comprises a burner plug attached to the leading end of a fuel supply cylinder a and having a slurry feed bore b and a plurality of spray medium feed bores c disposed circumferentially of the slurry feed bore b. Attached to the leading end of the burner plug d is a burner plate g having first mixing chambers f in which the slurry from a slurry feed chamber e and the spray medium from the spray medium feed bores c are initially mixed. Attached to the leading end of the burner plate g is a burner tip j having a secondary mixing chamber h in which the fuel mixture from the first mixing chambers f is secondarily mixed and having spray holes i.
The slurry fuel supplied through the fuel feed cylinder a is fed through the slurry feed bore b in the burner plug d, the slurry feed chamber e in the burner plate g and a plurality of radially outwardly extending feed holes l into the circumferentially disposed primary mixing chambers f and then initially mixed with the spray medium such as the steam or air supplied through fine holes m from the spray medium feed bores c. The fuel mixture is then forced to directly flow from the primary mixing chambers f into the secondary mixing chamber h and is secondarily mixed and the atomized slurry fuel is sprayed through the spray holes i of the burner tip j.
How the slurry fuel is sprayed is dependent upon the fact how the slurry fuel is mixed with the spray medium in the primary and secondary mixing chambers f and h and is specially dependent upon how the fuel slurry and the spray medium are mixed in the secondary mixing chamber h in which the slurry fuel and the spray medium mixed in the primary mixing chambers f are further mixed.
With the burner of the type described above, the primary fuel mixture (that is, the slurry fuel and the spray medium mixed in the primary mixing chambers f) is forced to directly flow into the secondary mixing chamber h under the expectation that the primary fuel mixture does impinge and reflect upon the inner wall n of the secondary mixing chamber h so that a high degree of secondary mixing effect may be attained. However, in practice, part of the primary fuel mixture is not satisfactorily mixed in the secondary mixing chamber h and discharged through the spray holes i.
In addition, in the conventional burner of the type described above, the burner plate g and the burner tip j merely abut against each other so that the primary mixing chambers f are nonuniformly misaligned from the spray holes i as shown in FIG. 2. As a result, the fuel mixture discharged out of the primary mixing chambers f cannot uniformly flow into the adjacent spray holes i. Furthermore, the ratio of the fuel mixture which is discharged through the spray holes i without impinging upon the inner wall n and then reflecting therefrom is increased so that a satisfactory degree of mixing effect cannot be obtained in almost all the cases.
Moreover, in the case of a burner of the type for spraying a highly abrasive slurry fuel such as CWM, it has been proposed to use a high abrasion-resistance ceramic material such as Si.sub.3 N.sub.4, SiC or the like to fabricate the parts including the spray holes i which are subjected to wear.
However, in this case, the ceramic materials have a low degree of resistance to thermal shock so that there arises a problem that the ceramic parts are cracked. Furthermore, the ceramic parts are cracked because of the difference in thermal deformation between the ceramic parts on the one hand and the burner tip j and the burner plate g which support such ceramic parts on the other hand.